Method of producing incandescent lamp cores or bases



Dec. 24, 1940. I G. VESZI METHOD OF PRODUCING INCANDESCENT LAMP CORES OR BASES Filed June 21, 1938 t lfarnlya articles, having reference more particularly to the Patented Dec. 24, 11940 MEIHOD PATENT OFFICE or PRODUCING meme scam: mm com S on. asses Giborvesll. Budapest, Hungary, asslgnor, by

nesne assignments, to General Electric Company, a corporation of New York Application June 21, 1938, Serial No. 215,030 In Germany June 25, 1937 This invention relates to electric lamps, or improvements therein, and aims to provide a desirable improvement in the construction of such core or base parts of the same.

The manufacture of electric lamp core parts or bases and especially small lamp bases, from hard glass or quartz glass is attended by substantial difliculties in spite of the fact that various methods are known for hermetically sealing into such glasses the current leads in the form of wires or thin foils made of refractory metals.

thickness, can be sealed directly into certain borosilicate glasses of high melting point and in the case of quartz glass, either a so-called intermediate glass which can be sealed (on the one hand) to tungsten and (on the other hand) to quartz can be used, or-a thin foil of a refractory" metal, such as molybdenum, can be employed instead of a wire" and the softened quartz glass allowed to collapse on to it in vacuo. Lampbases' of hard glass or' quartz'glass ar most necessary when the lamp bulb itself is made of such materials. Hard glass or' quartz glass bulbs are always used when, for any reason, it is preferable or essential to reduce the size of the bulb below a certain limit, as, for example, in the case of high pressure incandescent lamps, with filling pressures in excess of five atmospheres, incandescent lamps with a filling of mercury vapour etc. As it is precisely the reduction in the size of the bulb which compels the use of hard, glass or quartz glass as a material for thebulbs and bases, the importance of being able to make lamp bases of small size in these materials will very readily be apparent. Significant examples of the application of such bases are high pressure incandescent lamps with filling pressures of thirty, fifty or more atmospheres, and tubular hard glass or quartz glass bulbs 6 mm. or less in diameter. a

One object of the present invention is to provide a novel and simple method of making lamp bases of hard glass or quartz glass.

Another object is to provide an improved method of making lengths of two-duct capillary tubing in hard glass or quartz glass, to serve as starting material or stock for the manufacture of bases or stems for lamps as hereinbefore referred to.

Another object is to provide a method of making small, compact electric incandescent lamps of a kind adapted for operation with a high internal gas pressure and/or vapor pressure.

Yet another object is to provide lamp bases or For exam- 1 ple, tungsten wires, up to a millimetre or more in I stems of novel construction, for incorporation in electric incandescent lamps and a final object is .to provide a lamp of very simple and compact construction, such lamp being particularly well adapted for operation under a high internal pres- 5 sure of filling gas and/or vapor.

The lamp bases according to'the invention areproduced by sealing the current leads "simultaneously into one hard glass or quartz glass capillary tube having or formed with two ducts. 'Ijhe 10 sealing in of such leads may be effected under reduced (1. e. less than the usual) pressure and this expedient is indeed usually desirable when sealing foils of refractory metal directly into quartz glass. Particularly in the case of very small lamp bases, it is preferable, 'when using current leads in the form of metal foils, so to arrange the foils for sealing in that their broader faces (as distinguished fromtheir edges) confront one another and are parallel. 5

If, for example, tungsten .wires are used as leads and if the double capillary tube is made of borosilicate glass of suitable composition, the wires can be sealed directly into the glass and the sealing-in operation can be conducted inatmospheric air. On the other hand, the mode of pro-' cedure adopted when using a quartz glass double capillary tube may, for example, be as follows:' Two thin molybdenum foils, about ZO thick and 1 mm. wide, to the ends of which tungsten or .30 molybdenum wires of suitable shape and dimensions are welded, are introduced into the two ducts of a double capillary tube of quartz glass.

The capillary is sealed off at one end and evacuated and then, by heating the appropriate points 85 with an oxy-hydrogen flame, the quartz glass is allowed to collapse onto the the ,moiybdenum foils, after which the projecting ends of the tube can be cut oil.

The process according to the present invention 40 permits of working to fine limits of tolerance. even in the case of very small bases; it eliminates the risk of short circuits and it can be carried out rapidly. In cases where a quartzglass capillary tube is used in conjunction with leads made of i5 molybdenum foil, it has also the'g-reat advantage that the lamp base can be sealed intothe lamp bulb in atmospheric air. This is of great im portance, particularly in high, pressure lamps; wherein it is necessary to exercise meticulous 5 care in making the fused joint between the bulb of the lamp and the base thereof.

It should also be remarked that the double. capillary tubes required by the process of this invention can be manufactured easily, by sealing 5 I'he invention will now be more particularly 5 formed by or from the twoglass-elements of Fig. l

described with reference to the accompanying drawing, in which:

Fig. 11-isan enlarged cross sectional view'illustratingla tube and'ariinserted rod,. both of quartz 0 glass, in concentric arrangement between press plates which unite and shape the twoglass elements so'as together to forma double capillary I figure the references 2, 3, 4 again designate the tube; v V s Fig. 2 is a cross section through a capillary tube 1 pressed together; Y i a Fig. 3 is a longitudinal section of such a double capillary tube, having current leads inserted in its capillary ducts; this view beingJdrawn to a.

0 scale smaller than that of the preceding figures but the same as that of the following Figs. Hand '6;-

Figil 4 is a'cross, section taken on the line 3-3 of Fig..3'and is drawn to the same scaleas Figs. 1

5 .an y.

. 5.'shows lamp base structure produced by,

the process of the invention; and v Fig. 6 illustrates a finished incandescent lamp incorporating a base such as thatshownin Fig. 5. 0 Referring to this'drawing, l indicates a quartz glass tube from which theaforemention'ed double capillary or lamp base part is formed. Fig. 1

Y represents the method or manner, of formation "as last above described. That is, a. rod 1 of the 5 same, or also quartz glass, material is inserted into said tube, in this instance in a concentric relation. Upon heating said glass tube l sufliciently, the same can be pressed from opposite sides as by means of jawsprpress plates l0 and H until its diametrically opposed portions or walls meet and are flattened upon saidrod I into substantial fusion therewith. -In thisvery simple way a quartz glass bar with two longitudinalcapillary ducts, i. e. with channels on, opposite sides of the rod, is produced as shown in Fig. 2.

Said Fig. 2 shows the thus flattened tube l unitarily fused to. the rod 1, the said ductswhich are resultantly crescent shaped in cross section being designated'B and 8' respectively As will be seen in Fig. 3,-the two (composite) current leads, in this instance uncoated but which may be coated as with a glass that becomes intermediate (fused) between them and the capillary body in the hermetic seal later effected,

areinserted respectively inrthese capillary ducts 8 and 8', the internal diameter of which may, for example, be of the order of 1 mm. Each of said current leads consists of a molybdenum wire 2 and a tungsten inner lead or electrode 4, cono .nected by a molybdenum strip 3, whichmay for instance be 251/. thick and 0.8 mm. wide.

The double capillary tube thus composed is I next evacuated. This can be done in vacuum or any other suitable way, but if the capillary ducts -5 are closed at one nd, by closure of the tube -I as shown in Fig. 3, the other (open) end A-of the j tube can be connected directly to an air pump. The double capillary tube is then heated at the region of the line .B-B, in Fig. 3, until it collapses or flattens in fusibly upon itself and the ends are cut off at C and D, without severing the wires 2 and 4. The form of the lamp base thus obtained is shown in Fig. 5. In this last-named (which mayconveniently be referred to as electrodes) and the completed base or body 9 with said connected leads or electrodes is then fused into the quartzglass bulb 6, in air in the usual way. The isaid bulb is next evacuated at I 2 (through a pump tube not shown) and filled with a gas mixture, to a pressure higher than 10 at-' lmospheres, after which it is sealed off or closed.

Heretofore, current leads have been fused directly into quartz glass bulbs and, as the fusion has had to be conducted in vacuo, the process has proved to be very inconvenient in practice. It will be apparent-that the present invention affords a great and distinct advantage over this previously essential procedure in that only the sealing of the leads into the small double capillary tube has to be carried out under a vacuum, whereas the larger operation of sealing the con- 'ductor and base assembly into the bulb can be conducted at ordinary atmospheric pressure.

What I claim is:

1. The method of making a seal for electric lamps'and similar devices which comprises arranging a rod of vitreous material within a tube of vitreous material, heating said tube to render it plastic and then compressing it upon said rod in such a manner as to leave a plurality of longitudinally extending capillary ducts formed by unfused portions of the exterior surface of said rod and the interior surface of said tube, subsequently introducing metal conductors severally into said ducts, and then fusing the vitreous material and causing it to collapse around said conductors to form a'hermetic seal.

2. The method of making a seal for electric lamps and similar devices which comprises artube is removed fromlthe air pump and its two ranging a rod of vitreous material within a tube a of vitreousmateri'al, heating said tube to render it plastic and then applying pressure upon opposite sides of said tube to compress it upon said GABoR VESZI. 

